Electromagnetic waves may be transferred from place to place through a conductor. In wired transmission, the conductor is usually a wire or other solid substance. In wireless transmission, the conductor is usually an ambient substance, such as air, water, etc. In wireless connections a transmitter is usually used to transfer a wave and a receiver to receive a wave. A transceiver combines the functions of both transmitter and receiver in one system. A transmitter typically converts electrical energy into a signal, which is then broadcast via an antenna to a receiver's antenna. Repeaters, middle stations, etc. may be used as intermediates in the transmission to sustain the integrity of the transmitted wave.
The electrical energy input into a transmitter usually is modulated into a basic transmission or carrier signal by overlaying some intelligence upon the energy—speech, data, etc.—in the form of an information signal, and the receiver typically demodulates the modulated carrier signal, once received, into a copy of the initial intelligence sent by the transmitter.
In order to accomplish their function, transmitters and receivers are comprised of various building block components. An electromagnetic information signal (which may be generated from the intelligence in any number of ways, e.g., by one or more transducers, such as a microphone, or received from a modulator, such as an analog modem) to be propagated may be modulated onto a carrier signal using a mixer. The carrier wave itself is usually generated by an oscillator. An amplifier is usually used at one or more places in the transmitter circuitry to boost the signal strength, to provide power to active components, etc. Similarly, one or more filters are usually used as well, to clean up the input wave, the outputted signal, etc. An antenna is used to broadcast the signal, and a power supply will supply power as needed.
Various techniques may be used to actually transfer the intelligence. For example, electromagnetic waves representing the information signal in wireless transmission may be modulated into carrier signals by varying wave characteristics such as amplitude, frequency and phase, in an analog manner.
In certain embodiments of such systems, a segmented amplifier may be used to amplify the modulated signal for transmission. A segmented amplifier typically comprises a plurality of segments that are used to amplify an input wave by a predetermined gain. The type of segment is not limited and may comprise, for example, power amplifiers, current sources, etc. Each segment is typically controllable to be switched on or off by receiving an analog or digital control signal. The output from each segment may then be combined to create the output signal.
One way in which a segmented amplifier may be used, for example, is in the modulation/amplification of an input signal, such as in the amplitude modulation of a phase-modulated signal (although they may be used in other types of modulation and amplification as well). Each stage of the segmented amplifier has a pre-determined gain, and is switched on and off based upon a control signal based upon the amplitude of the input signal to provide a contribution of to the output signal.
However, switching the multiple stages of the segmented amplifier in this manner may cause the input impedance of the amplification system to shift. This shift in impedance may pull the phase modulating portion of the system off its desired carrier frequency, a phenomenon known as “load pull.”
Accordingly, it would be desirable to provide more efficient and precise transmitter, receiver and transceiver systems, methods and articles of manufacture, and particularly to reduce the input impedance shift created in segmented amplifiers due to the change in state of the segments to a small enough range that the carrier wave portion of a modulated signal inputted to the amplifier is not pulled off frequency during modulation.